The UK plans to safely dispose of its higher activity radioactive wastes deep underground in a geological disposal facility. Nuclear Waste Services (NWS) (formerly Radioactive Waste Management Limited (RWM)) is responsible for taking these plans forward, including demonstrating the long-term safety of geological disposal. Long term safety assessments necessarily include consideration of the biosphere, both to establish boundary conditions for the geosphere and engineered system as well as to provide estimates of potential impact of the relatively small amount of contamination that may reach the surface on very long time scales.
Quintessa has provided biosphere assessment support to the UK geological disposal programme since 2007. This has included multiple strands of work including:
- screening of radionuclides included within the national inventory to identify those warranting explicit consideration from the perspective of long term safety assessment;
- review of catchment scale hydrological modelling with MIKE SHE and SHETRAN to interpret the degree of mixing between shallow aquifers and deeper, potentially contaminated groundwater;
- review of biosphere characterisation activities undertaken in other national programmes;
- consideration of climate and environmental change, working with the University of Bristol in support of RWM’s participation in Working Group 6 of the IAEA’s MODARIA programme;
- updating RWM’s model for radionuclide releases to terrestrial and freshwater biosphere systems, including introduction of explicit representation of different climate states, including implementation of the model in GoldSim;
- developing new biosphere models to represent potential impacts arising from contaminant releases to estuarine, coastal and marine systems, including implementation of the model in GoldSim; and
- leading the authorship of the report describing the way in which the biosphere is treated within the 2010 and 2016 Disposal System Safety Case (DSSC).